The inflammatory and immune system is critical to the maintenance of lung structure and function. It does so by recruiting blood inflammatory and immune effector cells to the lung by production of chemotactic factors. Animal models have been established for beryllium lung disease. Studies of various genetic strains of animals have shown that the same strains of animals are sensitive to bleomycin induced lung disease and hypersensitivity pneumonitis. A new animal model of interstitial lung disease (the moth-eaten mouse) has been established as well as a new animal model in emphysema (the tight skin mouse). Evaluation of oxidant injury to the lung has shown that this is likely an important mechansim in lung damage induced by paraquat, high concentrations of oxygen, neutrophils, radiation, and bleomycin. Alveolar macrophages have been evaluated for the production of growth factors that induce fibroblasts to replicate. This growth factor has been characterized and its effect on lung fibroblasts detailed.